HELP PLEASE Time stretching audio

S

selsong

Member
I have a question I wonder if anyone can answer.

I recorded a piece of music at 110 bpm and did all the acoustic guitars etc. I then decided that the track should really be faster at 124 bpm. I have also found out that there is a great easy way of making each track play at the new tempo....by using the "sizing applies time stretch" tool. Most of the audio tracks sound fine, but some of them sound as though they are "wobbling"...this is the closest way I can describe what I hear

Does anyone know why this happens or do you know of any articles that explain why this happens? Also is there a way to time stretch with perfect results every time?

This is not urgent as I can simply re do the guitar parts affected, but Im really interested to know why this happens

Many thanks
 
selsong said:
I have a question I wonder if anyone can answer.

I recorded a piece of music at 110 bpm and did all the acoustic guitars etc. I then decided that the track should really be faster at 124 bpm. I have also found out that there is a great easy way of making each track play at the new tempo....by using the "sizing applies time stretch" tool. Most of the audio tracks sound fine, but some of them sound as though they are "wobbling"...this is the closest way I can describe what I hear

Does anyone know why this happens or do you know of any articles that explain why this happens? Also is there a way to time stretch with perfect results every time?

This is not urgent as I can simply re do the guitar parts affected, but Im really interested to know why this happens

Many thanks
Click to expand...

You should be able to select the algorithm used for time stretching (might depend on your Cubase version), e.g. Elastique Pro or soloist, etc. I think you'll get varying results depending on the source sound being stretched.
 
Are all the tracks you are stretching the same length? If not try arming all tracks and record a snippet at beginning and end. Bounce the tracks and try stretching them all at once.
 
That's a pretty big time shift. I'd re-record it unless it's way in the background noise of where you're going.
 
Also, if you have recorded two mics on the same instrument to two different tracks, that sort of time stretching will cause phase issues. You will need to group them together or turn them into a single stereo track.
 
Farview said:
Also, if you have recorded two mics on the same instrument to two different tracks, that sort of time stretching will cause phase issues. You will need to group them together or turn them into a single stereo track.
Click to expand...

Wait... I am curious as to how this works myself now.

I don't ever do this type of thing, but I am curious how time stretching of two tracks would go out of phase if they were stretched (in this case squashed) from the same same point? Does the algorithm employ it's own time base?

Is it possible that two mics out of phase (like a close and room mic 3'away) would not save the same offset if they were stretched/squashed from the same point?

Something I have personally never thought about but I may have to mess with it just so I know.
 
Each different algorithm handles things differently, but they all try to leave the transients intact while stretching or smashing the decay. Since each mic 'hears' something slightly different, the algorithm reacts differently to it, changing the timing enough to change the phase relationship.

Since the timing differences change constantly, there is no way to compensate.

In Nuendo (and I assume cubase), you can put all the tracks in a folder and time stretch the folder, which will apply the exact same changes to each track in the folder, thus keeping everything in sync.

For simple stereo micing, I just recorded it to a stereo track. (it's easier)

I used to have to do this with drums, and it was a nightmare before they let you time stretch the folder. Just imagine 13 tracks of a drum kit with all the tracks going slightly in and out of phase with each other all the time. I would have to mix the drum set down to a stereo file and time stretch that. If I didn't like the mix, I would have to go back to the original tracks, remix them down to a stereo track and time stretch again.
 
Farview said:
Each different algorithm handles things differently, but they all try to leave the transients intact while stretching or smashing the decay. Since each mic 'hears' something slightly different, the algorithm reacts differently to it, changing the timing enough to change the phase relationship.

Since the timing differences change constantly, there is no way to compensate.

In Nuendo (and I assume cubase), you can put all the tracks in a folder and time stretch the folder, which will apply the exact same changes to each track in the folder, thus keeping everything in sync.

For simple stereo micing, I just recorded it to a stereo track. (it's easier)

I used to have to do this with drums, and it was a nightmare before they let you time stretch the folder. Just imagine 13 tracks of a drum kit with all the tracks going slightly in and out of phase with each other all the time. I would have to mix the drum set down to a stereo file and time stretch that. If I didn't like the mix, I would have to go back to the original tracks, remix them down to a stereo track and time stretch again.
Click to expand...

That totally makes sense.

Thanks Jay. Hope it works for OP and I may try that in the future myself.
 
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